2 Answers
2

If you set the HISTTIMEFORMAT in bash your new entries get stored in the history file with a timestamp, older commands that don't have a timestamp (those before you ever set HISTTIMEFORMAT will display one and the same date-time-stamp (I assume the one from the first entry found with a real timestamp).

This problem should solve itself after your complete history has been updated in a few days.

You can look in ~/.bash_history to see what is the first line that has a date-time-stamp. Those are lines starting with a # followed by a (currently) 10 digit number.

I think this is a feature. As you just changed this setting, you can see from ~/.bash_history that the old command do not have a time-stamp stored. So for these commands, it will just assume the current time.

Try to put the export command in ~/.bashrc and execute a few command. You will see, that in ~/.bash_history an additional time-stamp will be save, which can then be displayed by history. So for new commands it should work as expected.

Thus: Not backwards compatible with commands executed in a different terminal window in the past.